Here \(\Delta \)  is the Laplace operator in \({\mathbb {R}}^3\) .
Henceforth, \(F \left( \alpha , \beta ;\gamma ;z\right) \)  is the hypergeometric function (see, e.g., [1]}). Our first main theorem gives for the Dirac operator the fundamental solution (retarded propagator) with
support in the forward cone.
